Question

I am needing help to solve this table. specifically the step 4 portion. My 2 compounds that I'm using for this experiment are 0.1 M NaHCO3 (acid) and 0.1 M Na2CO3. im having issues finding the concentration and pKa of everything.

thank you!

Step 1 hydrogen carbonate/carbonate (HCO3/003-) [NaHCO₃ and Nagco ₂] Initial Buffer: Pour 10 mL of the acid component of your buffer into a 50-ml beaker. Add 10 mL of the conjugate base of your buffer, and mix. Measure the pH of your mixture using a pH-meter. Calculate pK, for the acid. Step 2 Diluted Buffer: Add 20 ml water to your buffer mixture, and mix. Measure the pH of the diluted buffer. Calculate pK

Answer 1

Step 4

Total volume = 12 ml

Acid to conjugate base ratio = 1 : 5

Acid component is NaHCO₃

Moles of acid component = 0.1 M * 2 ml

[Acid] = 0.1 M * 2 ml/12 ml = 0.0167 M

Conjugate base is Na₂CO₃

Moles of conjugate base = 0.1 M* 10 ml

[conjugate base] = 0.1 M*10 ml/12 ml = 0.0833 M

pKa remains unaffected.

According to Henderson Hasselablch equation:

pH = pKa + log [Conjugate base]/[Acid]

= 10.57 + log(0.0833)/(0.0167)

= 10.57 + 0.698

= 11.27